Re: Alternative for vacuuming queue-like tables

Csaba Nagy <nagy@ecircle-ag.com> writes:
> I'm not sure how this operation can work in the presence of other long
> running transactions which did not touch the queue table yet, but it
> actually does work, I can confirm that. Is it violating MVCC maybe ?

Yes :-(.  I think you can get away with it if all your transactions that
use the queue table run in READ COMMITTED (not serializable) mode, and
if they work like

    BEGIN;
    LOCK queue_table IN some-suitable-mode;
    process queue table;
    COMMIT;

Grabbing the lock will ensure that CLUSTER finishes before any snapshot
is taken.

            regards, tom lane